The Democratic press. [volume] (Ravenna, O. [Ohio]) 1868-1901, 1887-08-04
Forests and Rainfall.


which covers the ground benee h t.
forest is Of conside 1h,C =. -.
On the top it consists altogether of
the decayed trunks, branches and
leaves, but it shades downward into
ordinary dark-colored soil, at depth
of few feet from the surface. This,
the decay zone of the forest, lies be-
tween the boughs of the air and the
branches of the roots. In it go on the
most important actions which take
place in our foFests-actions which af-
feet the history of land and sea. We
shall therefore have to consider it in a
somewhat painstaking way. The most
evident effect of this sheet of, decay
ing wood and moss which feeds on the
decay, is on the rainfall of the region
which it mantles. When, after a sea-
SON of drought, copious rain falls on
this spongy mass, the water is for a
long time absorbed in the interstices,
and does not flow to the rivers. Even
in times of heavy rain the water is
slowly yielded to the streams; after a
dry period of many weeks this sponge
retains q good share of water. A like
amount Of water falling on titled
fields or prairies slips quickly away to
the rivers and thence to the sea. The
first result is that when the land is
destitute of forests it sheds water like
house roofs, breeding floods after every
considerable rain, while in the forests
the rain is only slowly yielded to the
streams.
A second and less evident result of
the spongy character of the forest bed
is that, by hindering the escape of the
rain-water to the rivers, it increases
the actual rainfall OF the country. To
see the nature and importance of this
action we must turn aside for a mo-
ment to consider the origin of the
rain which falls upon the land. The
original source of this water supply is
the sea. which sends into the lands a
tolerably regular supply annually of
moisture. When this falls as rain or
snow, either of the two things may
happen-the water may go away di-
rectly to the sea, or it may return to
the atmosphere as .vapor, to be again
precipitated as. rain. The chance of
the re-eyaporation is determined by
the speed with which it flows to the
streams. From treeless region it
rapidly escapes; in an extensive region
of virgin forest it may again and
again pass from earth to air, and from
air to earth.
The columns of vapor, which in
times of summer rain may be seen
ascending from every great wood, af-
ford visible evidence of the effect of
the forests on rainfall. They also may
show the observer some of the most
beautiful phenomena of atmospheric
circulation. Ina summer rain shower
fho os.
cooler than it is in the recesses below
within the woods seeks to rise and es-
cape in great columns whenever there
is = wide gap between the branches;
as soon as it attains the cooler level
above, the moisture is condensed, and
the air, before transparent, becomes
surcharged with steam. To replace
this ascending air q broad current
drifts toward the emerging stream of
vapor, commonly from the highest
parts of the forest, where the air, ow-
than in the lower levels.
The repeated passage Of the moist
ure from earth to cloud and from cloud
to earth. greatly increases the amount
Of force which the rain applies in its
falling drops to the earth's surface;
but the rank vegetation protects the
surface from the erosion which it
would otherwise bring about. Even
the forest clad hillsides Of the Cum
berland mountains whore the soI I
on declivit.es = grsaf ess,
fer little wear as long as their natural
protection is. left to them. But as
soon as they are stripped of the gar
ment of wood which has been upon
the region ever since, in the far off
ages, they came from the depths of
the sea, they wear with great rapid
ity. Theerosion is limited, as they
are forest clad, to the stream beds, and
there is hindered by the innumerable
obstacles of the fallen trees and en-.
tangled driftwood. The brooks which
are strong enough to clear their beds
and cut into the earth and rock are
few in number; we may often, on the
fatter ground, find tracts of square
mile or so in area in which there is not
single stream that ever assails tRe
surface of the earth. As soon, how.
ever, as the forest mat is removed, the
surface becomes scanned with chan
nels; they often, ON the deforested sur.
face, increase one hundred fold in
their length and more than that meas
ure in their destructive power, Re.
lieFed of all restraint from fallen tim
Der, of the close knit roots which i'm
mesh the earth, they sweep precious
soil away toward the sea. In single
day titled field may lose from its
surface more soil than would be taken
from it in century of its forest state.
-Scrfbner's Magazine,